Contact structure for high voltage gas blast circuit interrupter

ABSTRACT

The cooperating stationary and movable contacts of a gas blast interrupter are each formed as elongated, tubular contacts which are slotted from one end to form contact fingers flexible at only one end. The fingers of the stationary contact engage the solid hub end of the movable contact, and the movable contact fingers slide on a stationary conductive tube.

United States Patent Aumayer Sept. 30, 1975 1541 CONTACT STRUCTURE FORHIGH 3,180,959 4/1965 MacNeill et a1. 200/148 R VOLTAGE GAS BLASTCIRCUIT 3,439,140 4/1969 Frowein 200/148 BV INTERRUPTER 3,441,692 4/1969Cromer et a1. 200/148 R [75] Inventor: Hansruedi Aumayer, Harleysville,FOREIGN PATENTS OR APPLICATlONS Pa. 613,844 12/1948 United Kingdom200/148 R [73] Assigneez :d-IT-E lnllperial Corporation, Spring PrimaryE aIm.er Robert S. Macon Ousa Attorney, Agent, or Firm-Ostrolenk, Faber,Gerb & [22] Filed: Sept. 19, 1973 Soffcn [21] Appl. No.: 398,871

[57] ABSTRACT [52] U S Cl 200/148 700/148 200/145 The cooperatingstationary and movable contacts of a [51] 1 33/64 gas blast interrupterare each formed as elongated, tu- [58] Fieid B 148 E bular contactswhich are slotted from one end to form 260/148 contact fingers flexibleat only one end. The fingers of the stationary contact engage the solidhub end of the l 5 6] References Cited movable contact, and the movablecontact fingers UNITED STATES PATENTS slide on a stationary conductivetube. 2,494,661 1/1950 Lzltour 200/148 R 7 Claims 6 Drawing Figures US.Patent Sept. 30,1975 Sheet 2 of5 3,909,571

HUI

US. Patent Sept. 30,1975

Sheet 3 of 5 l: 5-. Sb.

U.S. Patent Sept. 30,1975 Sheet 4 of 5 3,909,571

A I K a5 5' U.S. Patent Sept. 30,1975 Sheet 5 of5 3,909,57i

Ser. No. 398,870, filed Sept. CONTACT FOR HIGH VOLTAGE GAS BLAST CIR-CONTACT STRUCTURE FOR HIGH VOLTAGE GAS BLAST CIRCUIT INTERRUPTERRELATEDIAPPLICATIONS 'This application is related to copendingapplication 19, 1973, entitled CUIT BREAKER WITH TIME-DELAYED OPEN- ING,in the name of L. J. Kucharski; Ser. No. 398,869, filed Sept. 19, 1973,entitled MECHANICAL SUP- "PORTOF TRANSIENT RECOVERY VOLTAGE CA- of G. P.Guaglione et al., all of whichare assigned to the assignee of thepresent invention.

' BACKGROUND OF THE INVENTION This invention relates to high voltage gasblast interrupters, and more specifically relates to a novel cooperatingcontactstructure for high'voltage gas blast break- 1 ers.

High voltage gas blast breakers are well known to the art, and areshown, for example, in US. Pat. 3,526,734, issued Sept. 1, 1970,entitled DEAD TANK GAS BLAST CIRCUIT BREAKER WITH INTERRUPTER STRUCTUREIMMERSED IN LOW PRESSURE OF DEAD TANK, in the name of D. H. McKeough,and in jcopending application Ser. No. 175,507, filed Aug. 27, .1971,now issued as US. Pat. No. 3,823,289, entitled INTERRUPTER STRUCTURE FORCIRCUIT nBREAKER WITH INDIVIDUAL BLAST VALVES the sliding movablevcontact. and the conductive tube' which, slidably supports the movablecontact. This burning is believed to be due to bounce of the movablecontact fingers on the conductive tubeat the time of A furthersignificant advantage of the invention is that the contact fingers ofboth the stationary and movable contacts are relatively simplyconstructed and are self-biased to a given rest position. The fingersare then flexed to a greater diameter when they engage their respectivesolid cylindrical surfaces (the solid movable contact hub is engaged byand spreads the stationary contact fingers, and the outer surface of astationary conductive cylinder is slidably engaged by and spreads themovable contact fingers) to cause inherent strong contact biasing forcessince the contact fingers are elastically deformed and tend to return totheir rest position. Therefore, contact springs are avoided and, ingeneral, considerable economy and reliability is achieved with the useof the new contact structure.

BRIEF DESCRIPTION OF THE DRAWINGS FIGQl is an elevational view of acircuit breaker which employs the novel contacts of the presentinvention where a portion of the grounded support tank of the circuitbreaker has been removed to expose the various components therein;

f FIG. '2 is a cross sectional view through one of the interrupters ofthe circuit breaker of FIG. 1 and illustrates the novel contactstructure of the present invention. v I I FIG. 2a is a top planview ofthe stationary contact of 2. FIG. 2b is aside plan view of the movablecontact of FIG. 2. v

' FIG is a cross-sectional view of a contact structure constructedinaccordance with the invention without the time delay-feature of thecontact shown in FIG. 2

where thecontacts are in'the open position.

twhich incorporates'the present invention, as will be laterdescribed.,'lhe circuit breaker of FIG. 1 can, for

zexample, berated at 230,000 volts and at 63,000 amcontact separationbetween the movable and stationary interrupter contacts. Theconstruction of contacts of the prior art devices is also complicatedand required numerous complexly machined parts and separate contactfinger biasing springs.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the presentinvention, both the stationary and moving contacts are formed by tubularmented fingers of the movable contact slide over the outer surface of aconductive member. It has been found than when using this arrangement,substantially no shock wave is transmitted through the movable contactfingers at the time of contact separation.

Therefore, little or no burning due to contact bounce is experienced on:the movable contact fingers or the surface of the conductive support onwhich they slide.

peres.jConventionally, breaker will be a threephase' breaker and twoother and identical phases to the one shown in FIG. I will also beprovided.

In general, the circuit breaker phase of FIG. 1 is contained within agenerallyflattened spherical metallic "tank- 10 which is supported onmetallic frame angle -members 1 l and '12. Angles l 1 and l2 aresuitably reinforced and extend rearwardly and support additionalinvention is shown in adead tank configuration.

about 3 atmospheres. For purposes of the invention, any dielectric gasat any appropriate pressure could be used. For the'embodiment describedherein, the gas pressure within tank will be designated a relatively lowpressure. I

Each of the bushings 13 and 14 is further associated with currenttransformers l9 and 20, respectively, which may also be of any desiredconstruction.

A grounded flat support platform 21 is contained within the tank 10 andis supported from the bottom of tank 10 by welded support members, suchas bolts 22 and 23 and others not shown. Platform 21 sits on levelingnuts, such as nuts 24 and 25, respectively, of the support bolts. Theplatform 21 then serves as a level mount for the circuit interrupterequipment to be contained within tank 10. In the case of the breakershown in FIG. 1, four interrupters are to be connected in series withone another to define the circuit breaker voltage rating of 230 KV.Platform 21 supports two spaced hollow tubular insulation supportmembers 26 and 27,

.respectively, which further serve the purpose of high pressure gasreservoirs as is more fully described in copending application Ser. No.398,868, referred to above.

Each of the insulation support members 26 and 27 support, at their tops,respective blast valve housings 28 and 29 which, in turn, supportseries-connected interrupter units 30-31 and 3233, respectively. Each ofthe, interrupter units contains a pair of interrupter contacts which aresimultaneously opened in the presence of a blast of gas which assists inextinguishing the arc. It is to be noted that the tubes 26 and 27, blastvalve housings 28 and 29, and interrupters 30 to 33 are mechanicallysupported solely from the platform 21 and that none. of these componentsare supported from the bushings l3 and 14 or intermediate supports forthe interrupters 31 and 32.

The top of interrupter 30 is electrically connected to the stud 35 ofterminal bushing 13 through a flexible connection, which will be laterdescribed. The connectionbetween the top of interrupter 30 and stud 35is then covered by a corona shield 36.

The bottom of interrupter 30 is then connected through housing 28 to thebottom of interrupter 31. The top of interrupter 31 is connected throughflexible shunts 36a to the top of interrupter 32 with the tops ofinterrupters 31 and 32 and flexible connectors covered 7 by coronashields 37 and 38, respectively.

The bottom of interrupter 32 is then connected through the blast valvehousing 29 to the bottom of im terrupter 33. The top of interrupter 33is in turn connected to the stud 39 of bushing 14 by flexibleconnectors, such as flexible connectors 40=and 41. The connectionpreviously referred to between interrupter 30 and stud 35 incorporatesflexible connectors, such as the connectors 40 and 41. The connection tostud 39 I is then covered by the corona shield 42.

- FIG. 1 also shows voltage distributing impedances 43 and 44 connectedacross interrupters 30 and 33, re-

' spectively. Note that any suitable arrangement of parallel-connectedcapacitors or resistors could be used across the various interrupters 30to 33 in order to assure appropriate distribution of steady state andtransient voltages across the series-connected breaks.

-.FIG. 1 illustrates the provision of transient recovery voltagecapacitors 50 and 51 which are to be connected from either of the linesides of thebreaker to ground.

It will be noted that the flattened elliptical shape of tank 10 makesavailable free space in the outer central regions of thetank so thatthese capacitors can be mounted within this space without interferencewith the operation of the breaker or Without interference with thedielectric integrity of the breaker. The mounting of these capacitors isthe subject of copending application Ser. No. 398,869. a

It will be noted from FIG. 1 that the upper terminals of each ofcapacitors 50 and 51 are connected by relatively rigid conductors 52 and53 to the tops of interrupters 30 and 33, respectively, and are directlyand solidly connected to the bushing studs 35 and 39, respectively. Thebottoms of capacitors 50 and 51'are then mechanically and electricallyconnected to the tank wall 10 by the support and grounding brackets54and 55, respectively. V

The transient recovery voltage across the breaker is then controlled bythe capacitors 50 and 51in the manner generally set forth in US. Pat.No. 3,383,519, it being noted that each of capacitors 50 and 51 may havea value of approximately 0.0025 microfarads many other desired valueselected by the circuit designer.

The interior of the insulation reservoirs 26 and 27, which communicatewith the blast valve housings 28 and 29 and thence to the interrupters30 to 33 is at a relatively high pressure, such as 15 atmospheres of thesame dielectric gas which fills tank 10. I The major pressure source forthe breaker is an elongated cylinder which is filled with gas at highpressure and which may be covered with a heater blanket 61 to ensurethat the. gas temperature will always be sufficiently high to maintainit in a gaseous state. A protective shroud 62 covers the cylinder 60(which may extend the full length of all of the phases of the breaker),with portholes such as porthole 63 being available to permit maintenanceof the cylinder 60 and the blanket61. A suitable gas control system,'which need not be described to understand the present invention,provides suitable gas conduits and gas controls to conduct gas from thecylinder 60 through the conduit 64 which passes through a sealing plug65 in tube 66 which is secured to tank 10.

The high pressure conduit 64 then extends through a T-shaped member andinto conduits 67 and 68 as generally outlined by the arrows, in FIG. 1,such that high pressure gas is admitted to the interior of insulationreservoirs 26 and 27. As willbe later described, this gas is normallysealed at the blast valve housings 28 and 29 and high pressure gas isreleased through the interrupters 30 and 33 and into low pressure tankl0'only when the contacts of the interrupters are operated.

A suitable mechanical operating mechanism (not shown herein) is providedto mechanically actuate crank arms, such as crank arm 70 associated withtube 26, which drive operating rods which extend through the center ofsupport tubes 26 and 27 and upwardly to blast valve housings 28 and 29.Similar crank arms will be associated with each of the otherinterrupters of each phase of the breaker. Any conventional operatingmechanism, such as a spring operated mechanism or hydraulically operatedmechanism is then connected to each of the crank arms so that all blastvalves and 6 contacts can be simultaneously operated to either open orclose all interrupter contacts.

The specific details of one interrupter structure, such as theinterrupter 30 of FIG. 1 and aportion of the blast valve housing 28, areshown in FIG. 2. Referring now to FIG. 2, the interrupter and blastvalve are shown in cross-section and at the top of FIG. 2. Aswill belater described, interrupters 30 to 33 are subassembled units which canbe easily installed when the breaker is assembled. Thus, FIG. 2 showstwo flexible shunts 80 and 81 which have upper connectors 82 and 83which are appropriately bolted to the stud 35 of bushing 13, while theother ends of shunts 80 and 81 are bolted to an upper conductive adaptermember 84 of the interrupter 30. Note that the stud 35 does not serve asa mechanical support for the interrupter components.

The upper adapter 84 is bolted to a second adapter portion 85 with thetwo components 84 and 85 defining a volume 86 which leads to dischargeports such as the discharge port 87 which is positioned adjacent asimilar port 88 in the shield 36. Note the position of port 88 in FIG.1.

Additional ports are distributed around the periphery of shield 36 whichlead to similar openings defined between adapter members 84 and 85. Twofurther'ports of this general type are shown in FIG. 1 for shield 42 asthe ports 89 and 90.

The adapter member 84 further serves to threadably receive a tubulararcing terminal 91. Note that arcing terminal 91 has an opening 91atherethrough which extends upwardly so that some are venting can bedirectly vertically upward along the axis of the opening in arcingterminal 91. i

The use of flexible shunts to make the connection from the top ofinterrupter 30 to the terminal bushing stud 35 is made possible sincethe entire mass of interrupter structure 30 is supported on top of theblast valve housing 28. In prior art arrangements, such as thearrangement shown in US. Pat. No. 3,526,734, the stationary contactstructure of the interrupter is rigidly fastened to and carried by theend of the terminal bushing. This structure required careful alignmentof the interrupter components during assembly of the breaker and duringits operation. The structure shown in FIG. 2 eliminates the need foralignment during assembly of the circuit breaker and simple flexibleshunt members 80 and 81 are used to connect the top of the preassembledinterrupter 30 to the terminal bushing stud 35. Similar advantages applyto the connection between the top of interrupter 33 of FIG. 1 and theterminal bushing stud 39.

As previously described in connection with FIG. 1 the tops ofinterrupters 31 and 32 are connected in series by the flexible shunt36a. This is to be contrasted to the prior art arrangement of US.Pat.'No. 3,526,734 which required a separate support insulator extending.from the top of the housing which would physically carry the stationarycontacts for interrupters 31 and 32. By supporting interrupters 31 and32 from the blast valve housings 28 and 29, the separate supportinsulator and the alignment problems which were caused by the separatemounting of the stationary contacts of these interrupters areeliminated.

The interrupter 30 of FIG. 2 contains an elongated,

generally tubular stationary contact member 100 which has an upper solidring-shaped end 101 and slots which form segmented contact fingers, suchas fingers 102 and 103 in its other end. The segmented fingers ofcontact 100 are also shown in FIG. 2a which is a top end view of thecontact 100. It will be further noted that the ends of the segmentedcontacts. such as segmented finger contacts 102 and 103 terminate witharcing contact inserts which may have been formed as an insert ringwhich was brazed to the tubular contact member before the tubular memberwas slotted to form the segmented finger.

FIG. 20 further illustrates openings such as opening 104 in the solidflange 101 which accepts the bolts, such as bolt 105 which secures thestationary contact to adapter member 85. The bolts which pass throughthe openings in flange 101 of stationary contact 100 are threaded into aconductive ring which clamps the end side of flange 101 against adaptermember 85. Ring 110 serves as an upper support for the insulation tube111 which is the interrupter housing tube. Tube 111 may be made of anydesired material, such as an epoxy reinforced glass tube or the like.The upper end of tube 111 is suitably secured to and sealed with respectto ring 110 as by the securing key 112 and sealing ring 1 l3.

A set of bolt openings is formed in the inner diameter of ring 110 andthese bolt openings receive bolts, such as bolt 120, which threadablyengage ring member 121 and hold it in position. The exterior lowerportion of ring 121 is threaded and threadably receives the insulationbaffle 122 which may be of a suitable arc-resistant material such asTeflon, and serves as a guide for blast gases during the openingoperation of the interrupter, and as a means to protect or shield tube111 from the hot gases created during arc interruption. Baffle 122 alsocontains a plurality of thin, axially directed and circumferentiallyspaced fins, such as fin 123. These fins then prevent the formation of avortex in the gas blast which is guided by baffle 122.

The lower end of insulation tube 1 11 is fixed in a conductive supportring and is fixed therein and sealed thereto as by the key 131 andsealing ring 132. The ring 130 is, in turn, secured to a spider plate133 as by bolts, such as bolt 134, where the spider plate is formed of aconductive disk 134a having radially extending web sections such assections 135 and 136 which are joined to a centrally extending hollowconductive shaft 137. The shaft 137 then slidably receives the segmentedmovable contact 138 which is slidably engaged with the outer surface ofshaft 137.

The movable contact 138 consists of a generally tubularly shaped memberhaving a solid ring-shaped end 139 which receives a solid arcing ring140, with the lower end of contact 138 being segmented to form separatecontact fingers, such as fingers 141 and 142.

FIG. 2b shows a side plan view of the movable contact 138. The segmentedfinger elements 138 and 142 along with other similar fingers are flexedoutwardly from their normal relaxed position, and are therefor biasedinwardly and into sliding engagement with the outer surface of shaft137. The solid upper end 139 of movable contact 138 is movable into andout of rections through the arc, both through t'he center of stationarycontact 100 and the opening in arc terminal 91, and through the centralopening in contact 138 shown as opening 151.

The movable contact 138 is connected to an operating shaft 152 (whichcontains the opening 151) and the upper end of shaft 152 is providedwith flange 153. The flange 153 is engageable with the rear surface 154of the movable contact 138 and also receives a compression spring 155.The compression spring 155 is seated at its bottom on a ledge 156 of aspring retaining cylinder 157 which is threadably secured within theupper end of contact 138. The bottom of cylinder 157 slides within theinterior of conductive tube 137 and slides on a seal 158 within theshaft 137. The operation of the interrupter contacts described abovewill be later described after the blast valve arrangement and support ofthe interrupter from the blast valve housing 28 is described.

As is shown in FIG. 1, the blast valve housing 28 supports bothinterrupters 30'and 31. One lateral half of the blast valve housing 28is shown in FIG. 2 insofar as it relates to the support of interrupter30. It will be noted,'however, that the blast valve housing 28 issymmetric so that the same structure shown in connection withinterrupter 30 is provided on the opposite side of the center line 200in FIG. 2 for the support and operation of interrupter 31.

The insulation support member 26 of FIG. 1 is partly shown in FIG. 2 andit is seen that a metal end cap 201 is fitted over and sealed to the topof insulation tube 26.

- The metal cap 201 then serves as the support for the conductivesupport casting 202 of the blast valve housing 26. Casting 202 isprovided with a slot 203 therein for passing an arm 204 which isappropriately connected to the operating shaft 152 by the adapterfitting 205.

Cap 201 further serves to support ring 210 and circumferentiallydistributed posts such as posts 211 which are welded to ring 210. Theposts 211 are then welded to a valve seat plate 212 which carries thecutoff valve ring 213 of the blast valve as will be later described. Thevalve ring 213 is then held in position by closed and a current path isformed from terminal bushing stud 35 through the flange shunts and 81and into the adapter members 84 and 85 and the stationary contact 100.The current then transfers from stationary contact into the movablecontact 138 and the contact fingers 141 and 142 and into the conductivetube 137. From the conductive shaft 137 the current passes throughcasting 202 and then to interrupter 31 which is also supported on theblast valve housing 28. The current then proceeds through theinterrupters 31, 32 and 33 in the same manner and exits at bushing 14.

While the breaker is closed, the high pressure gas from within theinsulating support tube 26 fills the volume defined by the annular opengap between the bottom seal 213 and sleeve 243 and upwardly withinsleeve 222 and up to the valve seat 230. The interior of interrupter 30is at the relatively low pressure of the interior of tank 10, ascontrasted to the high pressure which is held at the valve seat 230. I

In order to open the circuit breaker, the circuit breaker operatingmechanism (not shown) is actuated to cause all of the operating rods,such as operating rod 220 to move simultaneously. The downward movementof rod 220 causes the sleeve 222 to move downwardly thereby to open theseal between the upper end of sleeve 222 and the valve seat 230. Thispermits the high pressure gas within sleeve 222 to move into thechamber.which contains spider members and 136 and upwardly through theannular channel 150 within the insulation tube 111. Thus, the pressurewithin the annular volume 150 begins immediately to increase.

At the same time, the downward movement of sleeve 222 causes the shaft152 to move downwardly and, initially, the upper flanged end 153 ofshaft 152 will cause the spring 155 to begin to compress. Thisintroduces an increasing downward force on the seal sleeve 157 and thuson the movable contact 138 which is connected to sleeve 157. Initially,however, the contact 138 does not move since the frictional forcesbetween the segmented fingers, such as fingers 141 and 142 of themovable contact against the outer surface of shaft 137 and thefrictional force between upper contact end 139 and the segmentedcontacts of the stationary contact 100 are sufficiently high to preventcontact motion. Ultimately, however, the spring force becomessufficiently high as to drive the movable contact 138 downwardly,thereby causing the separation of the contact 138 from the seg- Theupper end of blast valve sleeve 222 is engageable with upper blast valveseal 230 which is clamped in position by the clamping plate 231a. Thering-shaped valve seal 230 is carried on plate 231 which is generallysupported by a ring 232 which is an integral portion of I It is nowpossible generally to describe the operation 7 of the interrupter andblast valve of FIG. 2. With the components in the position shown, theinterrupter is mented fingers of the stationary contact 100 with a snapaction. Note that eventually the flange 153 will pick up shoulder 260 ofsleeve 157 if the movable contact does not begin to move under the forceof the compression spring 155 alone.

As the contact tip separates from the arcing contact finger portions ofthe segmented stationary contact 100, an arc is drawn between them.Substantial gas pressure has already been established within chamber andhigh pressure gas may begin to flow between the separating contacts evenprior to inception of the are as when the contact separation is somewhatdelayed by the lost motion connection between shaft 152 and the movablecontact 138.

As the contacts 100 and 138 separate, sulfur hexafluoride or a similarinterrupting gas passes rapidly through the annular region of contactseparation with a portion of the gas flowing into channel 151 andanother portion of the gas flowing upwardly and through i I on'the arcterminal 91 and the lower arc root will extendfrom the arcing tip 140.The are is quickly extinguishedunder the influence of the rapidly movingsulfur hexafluoride gas.

At the time the arc is extinguished; the sleeve 222 has r'novedsufficiently downward so that the shoulder 261 in the outside ofthe'sleeve 262 has picked up the lower sleeve 243's0 that the sleeve 243is moved downwardly and into engagement with valve seat 213. Thisoperation then cuts'off the further flow of high pressure gas from theinterior of cap 201 toward the interrupter,

thereby'to conserve thehigh pressure gas in the reservoir.

In order to reclose the breaker, the operating rod 220 is moved upwardlyso that the contact operating rod 152 moves upwardly to reclose thecontacts. Little or no gas blast is necessary during the closingoperation. Therefore, there is a time delay in the re-opening of theblast valve. Thus, the sleeve 243 remains sealed against seal 213 untilsleeve 222 and its outwardly facing extension 241 move to a sufficientlyhigh position that extension 241 engages the shoulder 242 of sleeve 243.At this point, the lower valve seat 213 is opened so that gas can flowfor the very short time until the upper end of sleeve 222 seats againstseal 230.

An important advantage of the contact structure described above is thatthe contact structure has few parts and no separate contact biasingsprings. Thus, the contact arrangement is inexpensive and reliable.Moreover, it has been found that by arranging the contacts so that thesegmented contact fingers extend from solid tubularends for both contact100'and contact 138, a shock wave is not transmitted through the movingcontact fingers 138 and 142 at the time of contact separation..Therefore, there is no bouncing of the segmented contact fingers 138and 142 on the outer surface of conductive shaft 137 so that there is noburning at this surface which burning would cause a high contactresistance.

A further advantage of the structure of FIG. 2 is that a time delaystructure is easily built into the movable contact of the segmentedcontact configuration to ensure that gas blast action has started beforethe contacts separate.

A further advantage of the contact configuration [shown is that, whenthe contacts open, the nozzle area for allowing rapid flow of gas fromannular region 150 is snapped open with the opening of the contacts,thereby allowing an extremely large passage for the flow of highpressure gas immediately after contact separation.

FIGS. 3 and 4 show a second embodiment of the contact structure of thepresent invention without the time delay feature of FIG. 2 which usesthe sleeve 157 and spring 155. In all other respects, the structure ofFIGS. 3 and 4 is similar or identical to the arrangement of FIGS. 2, 2aand 2b and similar components have been given similar identifyingnumerals.

FIG. 3 shows the contact structure of the invention in the openposition, where the operating rod 152 has been moved downwardly. Notethat the operating rod 152 is secured directly to contact 138 as bythreading to the interior in the upper end of opening contact 138.

In FIGS. 3 and 4, and as was the case in FIG. 2, the stationary andmoving contacts and 138, respectively, consist of a plurality ofsegmented contact fingers. The required contact force is, therefore,obtained by elastic deflection of the contact fingers from their restposition when the contacts engage their respective surfaces. Thus, noadditional contact springs are necessary to provide the needed contactpressure. Moreover, the design of FIGS. 3 and 4 has been found toprevent the transmission of a shock wave through the movable contactfingers at the time of contact separation so that there is no bouncingof segments 141 and 142 on the surface of shaft 137 and thus no burningat that surface.

Although this invention has been described with respect to its preferredembodiments, it should be understood that many variations andmodifications will now be obvious to those skilled in the art, and it ispreferred, therefore, that the scope of the invention be limited not bythe specific disclosure herein, but only by the appended claims.

The embodiments of the invention in which, an exclusive privilege orproperty is claimed are defined as follows:

1. In a circuit interrupter:

an integral, generally tubular stationary contact, one

end of said generally tubular contact being segmented in an axialdirection to define a generally circular cluster of contact fingers;

an integral, generally tubular movable contact movable into and out ofengagement with said stationary contact, one end of said generallytubular movable.contact being segmented in an axial direction to definea generally circular cluster of contact fingers, the opposite end ofsaid movable contact being a generally solid ring; said contact fingersextending for the major length of said generally tubular movable contactfrom said one end of said generally tubular movable contact to saidgenerally solid ring of said generally tubular movable contact; a

said tubular stationary and movable contacts being coaxial; said solidring end of said movable contact being movable into engagement withsurfaces of said circular cluster of contact fingers of said stationarycontact and having a diameter different than the diameter defined bysaid surface of said cluster of stationary contact fingers when they areunflexed, thereby to create a given contact pressure when said movableand stationary contacts are in engagement;

a generally stationary conductive tube supported in insulated relationwith respect to said stationary contact;

said tubular movable contact being coaxial with respect to saidstationary conductive tube and being in sliding contact engagementtherewith; said segmented movable contact fingers engaging a surface ofsaid conductive tube; said conductive tube having a diameter differentthan the diameter defined by the engaging surfaces of said movablecontact fingers when they are unflexed, thereby to create a givencontact pressure when said movable contact slides relative to saidconductive tube; whereby contact bounce of said movable contact fingersis substantially eliminated;

and an operating mcchanism for applying high forces over a relativelyshort time to said movable contact, thereby to move said movable contactinto and out of engagement with said stationary contact, and whereinsubstantially no shock force is transmitted to the region of slidingengagment between said movable contact fingers and said stationaryconductive tube when said movable contact moves out of engagement withsaid stationary contact; said operatingmechanism including an elongatedoperating shaft disposed coaxially with said movable contact andextending through the center of said stationary conductive tube, andhaving one end thereof fixed to said solid ring end of said movablecontact 2. In the circuit interrupter of claim 1, wherein saidstationary contact fingers engage and are flexed outwardly by the outersurface of said solid ring portion of said movable contact, and whereinsaid movable contact fingers engage and are flexed outwardly by theouter surface of said conductive tube.

3. In the circuit interrupter of claim 1, wherein said stationarycontact and stationary conductive tubes are connected to respectivecircuit interrupter terminals.

4. In the circuit interrupter of claim 1 which further includes gasblast means operable by said operating mechanism for producing a blastof gas between said stationary and movable contacts during theirmovement to a disengagedposition.

5. In the circuit interrupter of claim 4 wherein the interior of saidstationary contact and of said movable contact are permanently connectedto a relatively low pressure region, whereby gas flows from the exteriorof said stationary and movable contacts through the interiors thereof tosaid low pressure region during the operation of said movable contact toa disengaged position relative to said stationary contact.

. 6. In the circuit interrupter of claim 5, wherein said stationarycontact fingers engage and are flexed outwardly by the outer surface ofsaid solid ring portion of said movable contact, and wherein saidmovable contact fingers engage and are flexed outwardly by the outersurface of said conductive tube.

. 7. An electrical contact structure comprising:

an integral, generally tubular stationary contact,'one

circular cluster of contact fingers;

an integral, generally tubular movable contact movable into and out ofengagement with said stationarylcontact, one end of said generallytubularmovable contact being segmented in an axial direction to define agenerally circular cluster of contact fingers, the opposite end of saidmovable contact being a generally solid ring; said contact fingersextending from said one end of said generally tubular movable contact tosaid generally solid ring of said generally tubular movable contact; 5said tubular stationary and movable contacts being coaxial; said solidring end of said movable contact being movable into engagement withsurfaces of said circular cluster of contact fingers of said stationarycontact and having a diameter different than the diameter defined bysaid surfaces of said cluster of stationary contact fingers when theyare unflexed, thereby to create a given contact pressure when saidmovable and stationary contacts are in engagement; a generallystationary conductive tube supported in insulated relation with respectto said stationary contact; I said tubular movable contact being coaxialwith respect to said stationary conductive tube and being in slidingcontact engagement therewith; said segmented movable contact fingersengaging a surface of said conductive tube; said conductive tube havinga diameter different than the diameter defined by the engaging surfacesof said movable contact fingers when they are unflexed, thereby tocreate a given contact pressure when said movablev relative to saidtubular movable contact and having.

j one end thereof fixed to said solid ring end of said movable contact;said operating shaft extending through and being axially movablerelative to said" stationary conductive tube.

1. In a circuit interrupter: an integral, generally tubular stationarycontact, one end of said generally tubular contact being segmented in anaxial direction to define a generally circular cluster of contactfingers; an integral, generally tubular movable contact movable into andout of engagement with said stationary contact, one end of saidgenerally tubular movable contact being segmented in an axial directionto define a generally circular cluster of contact fingers, the oppositeend of said movable contact being a generally solid ring; said contactfingers extending for the major length of said generally tubular movablecontact from said one end of said generally tubular movable contact tosaid generally solid ring of said generally tubular movable contact;said tubular stationary and movable contacts being coaxial; said solidring end of said movable contact being movable into engagement withsurfaces of said circular cluster of contact fingers of said stationarycontact and having a diameter different than the diameter defined bysaid surface of said cluster of stationary contact fingers when they areunflexed, thereby to create a given contact pressure when said movableand stationary contacts are in engagement; a generally stationaryconductive tube supported in insulated relation with respect to saidstationary contact; said tubular movable contact being coaxial withrespect to said stationary conductive tube and being in sliding contactengagement therewith; said segmented movable contact fingers engaging asurface of said conductive tube; said conductive tube having a diameterdifferent than the diameter defined by the engaging surfaces of saidmovable contact fingers when they are unflexed, thereby to create agiven contact pressure when said movable contact slides relative to saidconductive tube; whereby contact bounce of said movable contact fingersis substantially eliminated; and an operating mechanism for applyinghigh forces over a relatively short time to said movable contact,thereby to move said movable contact into and out of engagement withsaid stationary contact, and wherein substantially no shock force istransmitted to the region of sliding engagment between said movablecontact fingers and said stationary conductive tube when said movablecontact moves out of engagement with said stationary contact; saidoperating mechanism including an elongated operating shaft disposedcoaxially with said movable contact and extending through the center ofsaid stationary conductive tube, and having one end thereof fixed tosaid solid ring end of said movable contact.
 2. In the circuitinterrupter of claim 1, wherein said stationary contact fingers engageand are flexed outwardly by the outer surface of said solid ring portionof said movable contact, and wherein said movable contact fingers engageand are flexed outwardly by the outer surface of said conductive tube.3. In the circuit interrupter of claim 1, wherein said stationarycontact and stationary conductive tubes are connected to respectivecircuit interrupter terminals.
 4. In the circuit interrupter of claim 1which further includes gas blast means operable by said operatingmechanism for producing a blast of gas between said stationary andmovable contacts during their movement to a disengaged position.
 5. Inthe circuit interrupter of claim 4 wherein the interior of saidstationary contact and of said movable contact are permanently connectedto a relatively low pressure region, whereby gas flows from the exteriorof said stationary and movable contacts through the interiors thereof tosaid low pressure region during the operation of said movable contact toa disengaged position relative to said stationary contact.
 6. In thecircuit interrupter of claim 5, wherein said stationary contact fingersengage and are flexed outwardly by the outer surface of said solid ringportion of said movable contact, and wherein said movable contactfingers engage and are flexed outwardly by the outer surface of saidconductive tube.
 7. An electrical contact structure comprising: anintegral, generally tubular stationary contact, one end of saidgenerally tubular contact being segmented in an axial direction todefine a generally circular cluster of contact fingers; an integral,generally tubular movable contact movable into and out of engagementwith said stationary contact, one end of said generally tubular movablecontact being segmented in an axial direction to define a generallycircular cluster of contact fingers, the opposite end of said movablecontact being a generally solid ring; said contact fingers extendingfrom said one end of said generally tubular movable contact to saidgenerally solid ring of said generally tubular movable contact; saidtubular stationary and movable contacts being coaxial; said solid ringend of said movable contact being movable into engagement with surfacesof said circular cluster of contact fingers of said stationary contactand having a diameter different than the diameter defined by saidsurfaces of said cluster of stationary contact fingers when they areunflexed, thereby to create a given contact pressure when said movableand stationary contacts are in engagement; a generally stationaryconductive tube supported in insulated relation with respect to saidstationary contact; said tubular movable contact being coaxial withrespect to said stationary conductive tube and being in sliding contactengagement therewith; said segmented movable contact fingers engaging asurface of said conductive tube; said conductive tube having a diameterdifferent than the diameter defined by the engaging surfaces of saidmovable contact fingers when they are unflexed, thereby to create agiven contact pressure when said movable contact slides relative to saidconductive tube; and an elongated operating shaft coaxially disposedrelative to said tubular movable contact and having one end thereoffixed to said solid ring end of said movable contact; said operatingshaft extending through and being axially movable relative to saidstationary conductive tube.